Starter bits for masonry drills



1961 M. L. GREEN ET AL 2,972,389

STARTER BITS FOR MASONRY DRILLS Filed Jan. 13, 1958 INVENTORJ MAX L. GREEN W/LZ/AM C K/IVARfl United Sw s STARTER BITS FOR MASONRY DRILLS V Max L. Green and William C. Kinard, Pasadena, Calif., assignors to Termite Drills, Inc., Pasadena, Calif., a corporation of California 7 Filed Jan. 13, 1958, Ser. No. 708,443

Claims. (Cl. 175-328) The invention relates to starter bits for masonry drills and more particularly to starter bits adapted to be driven by the drill for which they make the starting hole.

Conventional drill bits for masonry are designed so that the hole which is drilled has a flat bottom normal to the extent of the hole. The drill bit has cutting teeth inserted into its cutting face. These teeth are of a substance such as tungsten carbide which has very good wearing qualities. However, the angle at which the teeth are set with respect to the extent of drill, while optimum for progressing through the concrete or masonry, is not as effective in starting a hole as is a cutting edge tapered to a central point. Therefore, it is usually more efficient to use a separate starting bit to commence the drilling operation. We have developed a starting bit which can be used with a variety of different sized drills without sacrificing effective initial drilling characteristics in the masonry. V

The starter bit of the invention may be driven by the drill bit for which it is designed to start the hole. Such a starter bit may be used for starting holes for a plurality of drills within a given size range.

Conventionally, the cutting teeth of a masonry drill bit project transversely beyond a wall surface of the shank of the drill bit. This is true whether the masonry drill is a standard drill bit or a core bit type. The latter type has cutting teeth which may project not only beyond the outer portion of the shank but also into the hollow interior of the drill sh ank which accommodates the core formed by the cutting operation. The invention contemplates a starter bit for either type of drill which comprises a cylindrical coupling having a cutting portion at one end of the coupling and a plurality of longitudinal recesses in the coupling. The recesses. are adapted to engage the projecting portions of the cutting teeth so that rotation of thedrill rotates the starter bit.. The. coupling may be a hollow cylinder, in which case the drillbit fits within the coupling and teeth project into recesses in the wall of the hollow cylinder. The recesses may be located on the cylinder to engage the portion of the cutting tooth projecting from the cutting face of the drill shank. Alternatively, the coupling may be a cylindrical stern having longitudinal recesses in its outer periphery. I This latter starter bit embodiment is fitted within the core recess of the hollow drill shank. The cylindrical coupling of either starter bit embodiment may have a series of step por-- tions so that it may be used with two or more drill bit sizes.

The size of the desired starting hole is of course dependent upon the drill bit used. Therefore, the cuttingportion of the starter bit should be coordinated to thedrill bit size. If a multiple starter bit is used, the cutting blade may also be stepped and havea plurality of cutting edges. ting diameter equal to the diameter of one of the masonry drill bits to which the stepped cylindrical coupling Each separate cutting edge has. an. effective cut- A starter bit may be used which positions the drill bit. Such a pilot bit has a starter cutting blade which drills a center hole at the desired spot and acts as a rotating pivot fixing the drill bit while the teeth of the latter get started in the concrete. Such a starter bit can be driven by the drill teeth which project into recesses in the coupling of the starter bit.

One of the problems in using starter bits with masonry drill bits is that the starter bits become disassociated from the drill bits. Therefore, one embodiment of the invention provides means securing the starter bit to the drill bit for which the starter was designed. Preferably, the

means for holding the starter and drill bits together is a magnetized area on one of the bits adjacent its juncture with the other bit. The magnetic bond keeps the starter bit with the proper drill bit and also protects the cutting teeth of the drill bit by covering them during storage I or handling.

These and other advantages of the starter bits of the invention are apparent in the following specification and drawing, in which:

Fig. 1 is an elevation partly in section illustrating a masonry drill bit partly inserted into a starter bit embodying the invention;

Fig. 2 is a bottom plan section taken along line 2-2 of Fig. l;

Fig. 3 is an alternate embodiment of the invention showing a starter bit having a hollow cylindrical cou- Fig. 4 is a plan view of the starter bit of Fig. 3;

Fig. ,5 is a fragmentary elevational view partly broken away and illustrating a further. embodiment of the invention for use with a hollow core masonry drill bit;

Fig. 6 is a plan section taken along line 66 of Fig. 5; Fig. 7 is a fragmentary sectional elevation of a starter bit having recesses in the bottom of the coupling bore;

Fig. 8 is an elevational view of a still further embodi-..

ment of the invention adapted for use with more than one drill bit size;

Fig. 9 is an elevational view of a starter bit adapted for use with a plurality of masonry drill bit sizes; and

'Fig. 10 is an elevational view of a starter bit used in.

conjunction with the drill bit teeth to form a starting hole.

Figs. 1 and 2 illustrate a conventional masonry drill bit 11 having a plurality of cutting teeth 12 partly recessed in the cutting face of a drill bit shank 13. Each cutting tooth has a projecting portion 14 which extends transversely beyond the outer wall of the shank of the drill bit. .Thedrill bit extends into a starter bit 16 havingla hollow cylindrical coupling 18 and a cutting blade 20 with sharpened edges 21, 22.

The cylindrical coupling has a bore 25 into which the drill .bit is inserted. The bore has a plurality of longiv tudinal recesses 27 into which the projecting portions 14 bore.

teeth of the drill bit with which the starter bit is used. The proper position for operation is achieved whenthe teeth 12 shown in Fig. 1 rest in contact with the head 29 i of bore 25.

Figs. .3 and 4 illustrate an alternate embodiment of the 7 starter bit of the invention in which a hollow cylindrical. coupling 31 has a cutting blade 33 attached to one end thereof. An internal bore 35 is defined by a-wall 37 in extend from top to bottom which a plurality of slots 39 of the bore.

As in the embodiment of Figs. 1 and 2 and the starter i r bit of Figs. 3 and 4 is adapted to receive a masonry drill Patented Feb. 21,.1 96 1 bit having transversely oriented cutting teeth which project beyond the outer wall of the shank of the drill. The drill bit is inserted into the bore of the starter bit with the projecting portions of the cutting teeth in registry with the slots. The drill bit is pushed to the bottom of the bore and the teeth remain in registry with the slots. When the drill bit is rotated the engagement of the projecting teeth with the cylindrical coupling causes rotation of the cutting blade of the starter bit.

The cutting blade increases into the masonry or other material being drilled and cuts a hole having a diameter equal to the span of the cutting blade. The operator may stop the drilling operation when the maximum diameter is reached or may deepen the hole until a head 41 of the starter bit contacts the surface being drilled. At this point the starter bit is removed from the drill bit and the drilling operation continues with the more eflicient cutting teeth of the drill bit itself.

Figs. 5 and 6 illustrate an embodiment of the invention adapted for use with a hollow core drill bit. In these figures a masonry drill bit 45 having a shank 47 with a bore 49 open to the cutting face of the drill shank is engaged with a starter bit 51. The starter bit comprises a solid cylindrical stem 53 and a head portion 55 in which a triangular cutting blade 57 is fixed. The cutting blade has cutting edges 58, 59 which span a diameter equal to the effective cutting diameter of a plurality of cutting teeth 61 in the face of core bit 45. Portions of the teeth 61 extend beyond the drill shank intobore 49 of the shank.

The cylindrical stem of starter bit 51 has a plurality of longitudinal recesses 62 which extend the length of the stem. The number and orientation of the longitudinal recesses coincide with the number and orientation of the teeth of the core bit for which starter bit is adapted. The stem of the starter bit is inserted into bore 49 of the core drill so that the projecting portions of the cuting teeth register in the recesses of the cylindrical stern.

Fig. 5 also illustrates a preferred means for securing the starter bit to the masonry drill bit. A magnetized area 63 of the cylindrical stem of the starter bit (indicated by broken sectional shading) makes a magnetic bond between the starter bit and the masonry drill bit. The magnetic area is that portion of the starter bit adjacent the bore of the hollow core bit when in use. As can be seen in Fig. 5, when the starter bit is thus secured to the drill, cutting teeth 61 of the drill bit are protected from harm resulting from contact of those teeth with other hard objects. While the magnetic means for securing the two bits together is a preferred means, other Ways of securing the bits are not precluded.

Fig. 7 illustrates a drill bit 64 having a shank 64A from which a cutting tooth 65 projects downwardly. The drill bit lodges in a starter bit 66. The starter bit comprises a cylindrical coupling 67 having a bore 68 and a cutting portion 69. A transverse recess 70 in the head of the starter bit 66 receives the projecting portion of cutting tooth 65. When drill bit 64 is turned, the engagement of the tooth with the recess turns the starter bit.

While a single cutting tooth and transverse recess is shown, the bottom of the cylindrical coupling may have as many recesses as the fitted drill bit has teeth.

Figs. 8 and 9 illustrate embodiments of the invention.

in which a single starter bit is adapted to masonry drill bits of dilferent sizes. While both of the embodiments in these figures represent starter bits for use with hollow core drill bits, the same principle may be applied to starter bits having hollow cylindrical couplings for use with drill bits whose cutting teeth project outwardly beyond the shank of the drill.

In Fig. 8 a starter bit 71 having a triangular cutting blade 73 mounted in a cylindrical head portion 74 has a plurality of cylindricalstem portions 76; 77 an'd 78:

. 103 imbedded therein.

Cylindrical stem portion 76 is nearest the cutting blades. The stem portions 77 and 78 more remote from the cutting blade have lesser diameters than portion '76. These diameters correspond to the bores of the hollow drill bits for which the starter bit is to start the hole. Portion 78 is adapted to the smallest drill bit and portion 76 to the largest drill bit to be used with the starter bit.

Each of the cylindrical stem portions has a plurality of longitudinal recesses 81 which extend the length of the stem portion. The recesses coincide with the number of projecting teeth which the related drill bit has. The recesses are arranged about the periphery of each stem portion in the same orientation as the projecting teeth of the respective drill bit. While the previously described embodiments of the starter bit have been illustrated as for use with drill bits having three cutting teeth, the number of longitudinal recesses is not limited to. three. The number of recesses may coincide with the number of cutting teeth in any of the conventional masonry drills.

In Fig. 9 a starter bit 85 having a cylindrical coupling 87 substantially identical to the cylindrical coupling of Fig. 8 has a head portion 89 from which a cutting blade 91 projects. Remote from the head portion is a first cutting edge 93. The elfective cutting span of the first cutting edge is equal to the effective cutting diameter of the drill bit adapted to be fitted to a smallest cylindrical stem portion 87A of the cylindrical coupling. Less removed from the head portion are secondary cutting edges 95, 97. Connecting blade portions 99, 101 and 10-3 connect between cutting edges 9.3 and 95, 95 and 97, and 97 and head portion 89 respectively.

The cutting diameters effected by secondary cutting edges 95 and 97 correspond to the effective cutting diameters of the teeth of the drills adapted to register with stem portions 878 and 87C respectively.

Like the embodiment illustrated in Figs. 5 and 6, the starter bits of Figs. 8 and 9 are inserted into the bore of a hollow core drill bit. The embodiments of Figs. 8 and 9 may have magnetized areas which secure the starter bit to its respective drill bit. The starter bits are adapted to use with three different drill sizes. The starter bit of Fig. 8 has a cutting blade having an upper diametrial limit equal to the largest drill with which it is associated.

It is difficult for the operator to gauge the diameter of the starting hole if a hole less than the maximum diameter is required. There is no means in the starter bit of Fig. 8 for determining when the correct diameter for the drill bit to be used in the starting hole has been achieved.

This difiiculty is overcome in the embodiment of Fig. 9. The starter bit 85 has a cylindrical coupling for use with difi'erent drill sizes. Additionally, the cutting blade has means for indicating to the drill operator when the cutting blade commences a starting hole larger than re quired for the particular drill bit used.

Since a connecting blade portion separates each of the successive cutting edges, the action of the drill ditfers when a second or a third cutting edge contacts the ma sonry surface. Thus, if cutting edge 93 gives the correct diameter starting hole for which the associated drill bit calls, the incidence of secondary cutting edge 95 against the surface being drilled indicates to the operator that i the full depth of the correct diameter possible with the connecting blade portion has been achieved.

Fig. 10 illustrates a starter bit 101 which functions as a pilot pivot for incising a starting hole by the cutting teeth of the drill bit itself. Starter bit 101 has a cylindrical coupling 102, one end of which has a cutting blade The cutting blade has a lesser span than the outer cutting diameter of the drill bit.

A plurality of'longitudinal recesses 10-4 extend from an upper end 105*ofthe starter bit along the coupling to terminate at an annulus 106 between the cutting blade and the coupling. Cutting teeth of a drill bit such as bit 45 of Fig. 5 register in recesses 104 and bottom against a shoulder 108 of annulus 106.

The starter bit is driven by the drill bit. The cutting blade starts into the surface being drilled and forms an anchor for the drill bit. The latter then cuts its own starting hole as it rotates about the center established by the penetrations of the starter bit to the full length of its cutting blade.

The invention teaches a stanting bit which may be driven by the drill bit for which it provides a starting hole. The illustrative starter bits are capable of use with a large range of drill bit sizes, and with regular and hollow core types. A single starter bit may be used with a plurality of drill bits. The means of securing the bits together insures against loss of the starter bits and helps protect the cutting edges of the drill bit. Alternative forms other than those illustrated are possible within the scope of the invention.

We claim:

1. A starter bit, for masonry drill bits having a shank and at least one transversely oriented cutting tooth projecting from a wall surface of the shank, the starter bit comprising a cylindrical coupling having a head at one end thereof, a cutting portion extending outwardly from the head, means for securing the starter bit to the masonry drill bit, and a plurality of longitudinal recesses in the coupling adapted for engagement with the portion of the cutting tooth projecting from the shank surface so that rotation of the masonry drill bit imparts rotation to the starter bit.

2. A starter bit, for masonry drill bits having a shank and at least one transversely oriented cutting tooth projecting transversely from a Wall surface of the shank, the starter bit comprising a hollow cylindrical coupling terminating in a closed head, having a cutting portion extending outwardly from the head, means for securing the starter bit to the masonry drill bit, and a plurality of iongitudinal recesses in the Walls of the coupling adapted for engagement with the portion of the cutting tooth projecting from the shank surface so that rotation of the masonry drill bit imparts rotation to the starter bit.

3. A starter bit, for a drill bit which has a shank and at least one substantially transversely projecting cutting tooth, comprising: a cylindrical coupling having a cutting surface at one extremity thereof; and at least one recess on a curved surface of said coupling for each transversely projecting cutting tooth of said drill hit, each recess being adapted for engagement with a projecting tooth of said drill bit, whereby rotation of the drill bit imparts a rotary motion to the cutting surface of said starter bit.

4. A starter bit, for a masonry drill bit which has a shank and at least one substantially transversely projecting cutting tooth, comprising: a hollow cylindrical coupling having a cutting surface substantially closing one end thereof said hollow cylindrical coupling being adapted to enclose the transversely projecting cutting teeth of the masonry drill bit, and at least one recess on the inner curved surface of said starter bit for each transversely projecting cutting tooth of said masonry drill hit, each recess being adapted for engagement with a transversely projecting cutting tooth of said masonry drill bit, whereby rotation of said masonry drill bit imparts a rotary motion to the cutting surface of said starter bit.

5. A starter bit, for a masonry drill bit which has a shank and at least one substantially transversely projecting cutting tooth extending therefrom, comprising a hol low cylindrical coupling having a cutting surface substantially closing one end thereof, said hollow cylindrical coupling being adapted to enclose at least a portion of the shank of the drill bit, and at least one recess on the inner surface of said starter bit, said recess being adapted for engagement with a transverse cutting tooth of said masonry drill bit, whereby rotation of said masonry drill bit imparts a rotary motion to the cutting surface of said starter bit.

References Cited in the file of this patent UNITED STATES PATENTS 2,550,775 Clark May 1, 1951 2,639,122 Petersen May 19, 1953 2,673,717 Bacon Mar. 30, 1954 2,816,737 Kinard et a1. Dec. 17, 1957 (SEAL) UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No, 2,972,389 February 21, 1961 v Max L. Green et al.

It is hereby certified'that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 10, for "increases" read incises Signed and sealed this 25th day of July 1961,

Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents 

